Electric watch



Nov. 21, 1961 H. EPPERLEIN 3,010,075

ELECTRIC WATCH Filed Sept. 10, 1958 Fig. 2.

INVENTOR He/muf E pper/e/n io/Wm; f 0826M ATTORNEYS 3,010,075 PatentedNov. 21., 1961 United States Patent Ofiice This invention relates toelectric watches and more particularly relates to the driving device forsmall watches of the wrist watch type. g

In the powering of electric watches, it has been proposed to utilise anarrangement in which an armature :consisting of apermanent magnet -isarranged in an air jgap between the polesof an iron core having twocoils ;wound thereon. These two coils form the input-and output coils ofan amplifier which is controlled by the currents induced in the inputcoil "and, develops a current in the output coil which powers thearmature. Such a device might be provided with a brake limiting therotational speed of the armature which runs constantly in a singledirection like the armature of a conventional motor with the directionof rotation being determined by the direction in which the armaturestarted to rotate.

The present invention relates to a device for driving electric watcheswhich is characterized by a balance wheel similar to those used in anordinary spring watch and is provided with a conventional hairspring. Inaddition to these conventional features, the balance wheel is alsoprovided with a bar of soft iron or other magnetic material extendingparallel to the horizontal plane of the balance wheel. This bar isinstalled in the air gap 7 between the poles of an iron core having twocoils wound thereon. The two coils constitute the input and output coilsrespectively of an amplifier acting in the manner of a blockingoscillator and controlled by the current induced in the input coil withthe output current driving the balance wheel. According to theinvention,

the bar of soft iron creates a variable coupling between the input andoutput circuits depending upon the momentary position of the balancewheel. The magnitude of oscillation of the balance wheel is determinedin a well known manner by the moment of inertia of the wheel, includingits bar of soft iron, and by the power which is stored in thehairspring.

It is accordingly a primary objectof the present invention to provide animproved device for'powering a small electric watch.

It is another object of the invention to provide an improved device forpowering an electric watch utilizing a transistor in a blockingoscillator type circuit.

It is still another object of the invention to provide an improveddevice for powering an electric Watch comprising a magneticmemberoscillating with the balance wheel and installed in the air gap of amagnetic core having two coils which constitute the input and outputcoils respectively of a transistor amplifier operating in the manner ofa blocking oscillator.

These and further objects and advantages of the invention will becomemore apparent upon reference to the following specification and claimsand appended drawings wherein:

FIGURE 1 is a plan view, partly diagrammatic, showing an electric watchpowering device of the type comprehended by this invention; and

FIGURE 2 is a partial vertical cross-section showing the construction ofthe balance wheel and magnetic bar.

Referring to FIGURE 1, there is shown at 10 a generally semi-circulariron core having pole shoes 11 and 12 and having an input coil 13 and anoutput coil 14 wound thereon. The input coil 13 may, as an example,consist of approximately 12,000 turns of a wire 0.03 mm. in diameterwhile the output coil 14 may comprise approximately 18,000 turns of awire of the same diameter. The self capacity of the two coils 13 and 14is indicated in FIGURE 1 by the capacitors 13a and 14a which are shownconnected into the circuit by means of broken lines. i I

The amplifier itself consists of a PNP contact transistor 15 whoseemitter is indicated at E, whose collectoris indicated at C and whosebase is indicated at B. This transistor may be of the C0340 type,manufactured by the lntermetall Company ofGermany. Other equivalenttransistor types may of course be utilized. h

This transistor provides "a current amplification of more than 30 whenconnected in the emitter circuit which is shown. It is necessary thatnatural oscillation be prevented and thus in some instances it maybedesirable, although not essential, to connect a resistance 16 .be-

- tween the emitter and base as shown in FIGURE 1,

depending upon the temperature. The emitter and base are connectedrespectively to the upper and lower terminals of the input coil 13 whilethe collector is connected to the lower terminal of the output coil 14.The upper terminal of the output coil 14 and upper terminal of the inputcoil 13 are respectively connected to the negative and positiveterminals of a small primary battery 17 which may, as an example, have avoltage of 1.5 volts.

Mounted between the pole shoes 11 and 12 and supported by a conventionalbridge 24 and pillar plate 25 is a balance wheel 18 which is of the sameconstruction as that found in conventional watches. Also conventional isa hairspring 19 connected at one end to the balance staff 22 and at theother end to. a suitable stud 22a on the bridge 24. Suitable jewelbearings 23 may be provided for cooperating with the pivots 21 on thebalance staif 22.

Mounted on the balance staff 22 below the balance wheel 18 is the softiron bar 20 which extends from one pole piece "11 to the other polepiece 12 as is seen in FIGURE 1.

The device shown in the figures of the drawings operates in such amanner that he bar of soft iron creates a variable coupling between theoutput coil 14 and input coil 13 of theampliiier. This coupling isrelatively strong when the bar of soft iron occupies the position shownin FIGURE 1 but is relatively weak when the bar is withdrawn from thisposition. In operation, the amplifier goes into a strong oscillationwhich causes a brief magnetization of the bar when it is in the positionshown in FIGURE 1, and the balance wheel is at this time pushed out ofthis line by the action of the power created between the ends of the barand the pole shoes at each passage through this position. This eifectresembles that of a blocking oscillation inasmuch as such an oscillatoralso undergoes an intermittent large amplitude oscillation.

The duration of the oscillation of the balance wheel is determined byits moment of inertia and by the power of the hairspring 19 as in thecase of an ordinary watch equipped with a balance wheel. Of course, themoment of inertia of the bar 20 supplements that of the balance wheel indetermining the period of oscillation.

The energy of oscillation which is lost through friction is replenishedfrom the battery 17 by means of the amplifier so that the balance wheelundergoes undamped oscillations which extend through an angle ofapproximately 310 degrees.

The invention may be embodied in other specific form's without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by; theappended claims rather than by the foregoing description, and allchanges which come Within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. In a battery powered watch having a balance staff and hairspring, amagnetic bar mounted on said balance 'stafi and extending diametricallythereacross for oscillation therewith, a magnetic core having oppositepole pieces diametrically opposed with respect to said balance staff andin close proximity to the ends of said bar, said c'ore being generallyarcuate in form, an input coil of said input coil adjacent said polepieces being connected to the base of said transistor, the other end ofsaid input coil being connected to the emitter of said transistorand tothe positive terminal of said battery, the end of said output coiladjacent said pole being connected to said collector, the other end ofsaid output coil being connected to the negative terminal of saidbattery, and said bar forming a variable coupling between the input andoutput circuits of said amplifier whereby it acts as an oscillator withthe input coil controlling the oscillator and the output coil drawingpower therefrom to sustain the balance staff in oscillation.

2. A battery powered watch as set out in claim 1 including a resistorconnected between the emitter and base of said transistor to preventnatural oscillation.

References Cited in the file of this patent UNITED STATES PATENTS2,769,946 Brailsford Nov. 6, 1956 2,831,114 Van Overbeek Apr. 15, 19582,845,772 Beyner Aug. 5, 1958 2,877,399 Shaull Mar. 10, 1959 FOREIGNPATENTS 785,749 Great Britain Nov. 6,-1957

